He pretty much invented the zombie subgenre as we know it. Most zombie movies still conform to the rules set forth in Night of the Living Dead.

Romero would go on to make several more Dead movies with the all time zombie classic Dawn of the Dead, followed by Day of the Dead, and later on, Land of the Dead, Diary of the Dead, and Survival of the Dead. I read a report he was working on a 7th entry, but I'm thinking that will no longer happen.

George Romero was savagely good at Horror. I think my favourite zombie movie of all time is Day of the Dead. It is so bleak, so beautiful. Love it. He lost his touch in later years but his work will be remembered for as long as there are zombies populating our consciousness.